"I am puzzled that the UCI has waited until the very last moment to appeal," CAS's Matthieu Reeb told Reuters. "We lost a few precious weeks because of that."

CAS is awaiting formal notification from the UCI of its decision to appeal. Whether the World Anti-Doping Agency (WADA) will join the UCI's appeal remains to be seen. The international organization has 21 days left to decide.

"If the parties really want a quick decision, 'we can arrange that'," said Reeb, who added that he is expecting a "fierce defence" from Contador's lawyers.

"I am pessimistic we can make a ruling before the end of June." The Tour de France will start on July 2.

Contador is eligible to compete while the appeal is pending. He has conistently denied doping and defended himself by saying the Clenbuterol got into his system after ingesting contaminated meat.